linux-kernel - Re: [PATCH 1/5] media: uapi: videodev2: Add support for AV1 stateful decoder

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Message-ID: <dfe8bdbbf12ec54c7a27888f911082ab63d6030f.camel@ndufresne.ca>
Date: Thu, 02 Oct 2025 15:42:00 -0400
From: Nicolas Dufresne <nicolas@...fresne.ca>
To: Deepa Guthyappa Madivalara <deepa.madivalara@....qualcomm.com>, Mauro
 Carvalho Chehab <mchehab@...nel.org>, Vikash Garodia
 <vikash.garodia@....qualcomm.com>, Dikshita Agarwal	
 <dikshita.agarwal@....qualcomm.com>, Abhinav Kumar
 <abhinav.kumar@...ux.dev>,  Bryan O'Donoghue	 <bod@...nel.org>
Cc: linux-media@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH 1/5] media: uapi: videodev2: Add support for AV1
 stateful decoder

Hi,

Le mercredi 01 octobre 2025 à 12:00 -0700, Deepa Guthyappa Madivalara a écrit :
> Introduce a new pixel format, V4L2_PIX_FMT_AV1, to the
> Video4Linux2(V4L2) API. This format is intended for AV1
> bitstreams in stateful decoding/encoding workflows.
> The fourcc code 'AV10' is used to distinguish
> this format from the existing V4L2_PIX_FMT_AV1_FRAME,
> which is used for stateless AV1 decoder implementation.
> 
> Signed-off-by: Deepa Guthyappa Madivalara <deepa.madivalara@....qualcomm.com>
> ---
>  Documentation/userspace-api/media/v4l/pixfmt-compressed.rst | 8 ++++++++
>  include/uapi/linux/videodev2.h                              | 1 +
>  2 files changed, 9 insertions(+)
> 
> diff --git a/Documentation/userspace-api/media/v4l/pixfmt-compressed.rst
> b/Documentation/userspace-api/media/v4l/pixfmt-compressed.rst
> index
> 806ed73ac474ce0e6df00f902850db9fd0db240e..043ec57d7d48a36005f2a0121a5bc7b733d0
> 6590 100644
> --- a/Documentation/userspace-api/media/v4l/pixfmt-compressed.rst
> +++ b/Documentation/userspace-api/media/v4l/pixfmt-compressed.rst
> @@ -274,6 +274,14 @@ Compressed Formats
>          of macroblocks to decode a full corresponding frame to the matching
>          capture buffer.
>  
> +    * .. _V4L2-PIX-FMT-AV1:
> +
> +      - ``V4L2_PIX_FMT_AV1``
> +      - 'AV10'
> +      - AV1 compressed video frame. This format is adapted for implementing
> AV1
> +        pipeline as stateful video decoder. The decoder expects one Temporal

I would do a small edit here. Instead of stating that this is for decoders, I
would rather document the intended behaviour for video codec. This way the spec
remains open for CAPTURE driver to produce AV1 in the future, or OUTPUT driver
consuming it in the future.

> +        Unit per buffer from OBU-stream or AnnexB.
> +        The encoder generates one Temporal Unit per buffer.

Otherwise I'm fine with the proposal of using TU aligned. Similar to other
codecs, we can always allow adapting the behaviour using controls, keeping this
as the mandatory default so it just works regardless of the HW we run on.

regards,
Nicolas

>  .. raw:: latex
>  
>      \normalsize
> diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
> index
> becd08fdbddb857f8f2bf205d2164dc6e20e80b2..4c07ad6afd45d6a56d19d65fd25f091d8172
> 5823 100644
> --- a/include/uapi/linux/videodev2.h
> +++ b/include/uapi/linux/videodev2.h
> @@ -775,6 +775,7 @@ struct v4l2_pix_format {
>  #define V4L2_PIX_FMT_H264_SLICE v4l2_fourcc('S', '2', '6', '4') /* H264
> parsed slices */
>  #define V4L2_PIX_FMT_HEVC_SLICE v4l2_fourcc('S', '2', '6', '5') /* HEVC
> parsed slices */
>  #define V4L2_PIX_FMT_AV1_FRAME v4l2_fourcc('A', 'V', '1', 'F') /* AV1 parsed
> frame */
> +#define V4L2_PIX_FMT_AV1      v4l2_fourcc('A', 'V', '1', '0') /* AV1
> (stateful) */
>  #define V4L2_PIX_FMT_SPK      v4l2_fourcc('S', 'P', 'K', '0') /* Sorenson
> Spark */
>  #define V4L2_PIX_FMT_RV30     v4l2_fourcc('R', 'V', '3', '0') /* RealVideo 8
> */
>  #define V4L2_PIX_FMT_RV40     v4l2_fourcc('R', 'V', '4', '0') /* RealVideo 9
> & 10 */

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